Trump has been intrigued by the idea of tariffs for years. In his 2011 book, Time to Get Tough, he proposed a 20 percent tax on imported goods.
More recently, Trump has floated even bigger tariffs as a possible remedy for the nation’s international-trade malaise.
• During his presidential announcement speech, Trump suggested that if a company like Ford built a factory in Mexico, he would respond by calling Ford’s CEO to say, "Every car and every truck and every part manufactured in this plant that comes across the border, we’re going to charge you a 35-percent tax."
• In an interview with the New York Times editorial board, Trump said he would support a 45 percent tariff on Chinese exports to the United States.
• In a Republican debate, his then-presidential rival Ted Cruz brought up his past comments on trade. Trump responded, "The 45-percent is a threat that if they don't behave, if they don't follow the rules and regulations so that we can have it equal on both sides, we will tax you. It doesn't have to be 45, it could be less. But it has to be something because our country and our trade and our deals and most importantly our jobs are going to hell."
http://www.politifact.com/truth-o-meter/article/2016/jun/21/donald-trump-has-floated-big-tariffs-what-could-im/